1. Field of the Invention
The present invention relates to an organometallic compound capable of improving vaporization stability, its synthesis method, along with a solution raw material and metal-containing thin film containing said compound. More particularly, the present invention relates to an organometallic compound suitable for use as a raw material for producing Si—O—Hf thin films, HfO2 thin films, Si3N4 thin films and so forth by metal organic chemical vapor deposition (MOCVD), its synthesis method, and a solution raw material and metal-containing thin film containing said compound.
2. Description of the Related Art
SiN-based insulating films are widely used for wafer passivation films. In the production of SiN-based insulating films, deposition is carried out at low temperatures by plasma CVD so as not to damage the Al wiring or other low-melting-point material layer formed on the substrate. Examples of raw material gases used for this purpose include silane/ammonia mixed gas and silane/nitrogen mixed gas.
However, the step coverage of SiN-based insulating films formed by plasma CVD are unable to accommodate the increases in surface level differences accompanying the reduced size of semiconductor devices and the use of multiple wiring layers, thereby resulting in the formation of voids and increased susceptibility to crack formation.
Therefore, a CVD method using an organic Si compound for the raw material gas has been studied and developed as a method for depositing SiN-based insulating films having superior step coverage. When deposition is carried out using for the raw material gas a compound having bonds between Si atoms and N atoms (Si—N bonds) such as [(CH3)2N]4Si, an SiN-based insulating film can be deposited efficiently due to the presence of the Si—N bonds. In addition, SiN-based insulating films that offer superior step coverage are believed to able to be deposited since intermediate products in which Si—N bonds persist easily form high molecular weight compounds and exhibit a high degree of fluidity as a result of hydrocarbon groups being severed from the organic Si compound during deposition. However, there has also been concern over deterioration of insulating durability as well as deterioration of moisture resistance and corrosion resistance due to the presence of residual hydrocarbon groups.
As a measure for solving the aforementioned problems, an insulating film formation method has been disclosed that is comprised of a deposition step in which an insulating film is deposited on a substrate by CVD using an organic Si compound having bonds between Si atoms and N atoms, and a post-treatment step in which the insulating film is subjected to plasma treatment in an atmosphere of post-treatment gas at least containing nitrogen atoms within its molecules (see, for example, Japanese Unexamined Patent Application, First Publication No. 7-235535). SiN-based insulating films and SiON-based insulating films obtained by this insulating film formation method are capable of inhibiting incorporation of hydrocarbon groups while ensuring superior step coverage.
On the other hand, although silicon oxide films are used as highly dielectric insulating films, accompanying the higher levels of integration of LSI in recent years, silicon oxide films have become increasingly thin. Since tunnel current flows through thin films having a film thickness of 100 nm or less resulting in a decrease in insulating effects, further reductions in thickness of silicon oxide films are reaching their limit.
Consequently, there is a need for a gate insulating film to take the place of silicon oxide films, and Hf-containing thin films, and particularly HfO2 and HfO2—SiO2, are attracting attention as possible candidates. Although examples of production methods of these thin films include sputtering, ion plating, coating thermal decomposition, sol gel and other MOD methods, MOCVD is being studied as the optimal thin film production process due to its superior composition controllability and step coverage, and its compatibility with semiconductor production processes.
An example of a method for depositing Hf-containing thin films by MOCVD include a method in which an organic raw material exemplified by at least one type or a plurality of types of M[N(C2H5)2]4 (wherein, M represents a metal (including Si) element) is introduced into the deposition chamber followed by deposition of a metal (including alloys) film or metal compound film by CVD and heat treatment at a temperature higher than the temperature used during deposition following deposition (see, for example, Japanese Unexamined Patent Application, First Publication No. 2002-167672). According to the aforementioned deposition method, metal or metal compound can be deposited with satisfactory controllability and uniformity even if there are irregularities in the deposited surface of a semiconductor device or electronic device, thereby enabling the production of semiconductor devices and electronic devices having satisfactory performance.
However, although halogens and so forth are not contained in the compositions of the organic Si compound having bonds between Si atoms and N atoms disclosed in Japanese Unexamined Patent Application, First Publication No. 7-235535 or the M[N(C2H5)2]4 indicated in Japanese Unexamined Patent Application, First Publication No.2002-167672, during the synthesis reaction, chlorine and water are always contained as impurities. Since chlorine and water are not easily reduced even when ordinary purification is carried out, precipitates caused by the chlorine and water end up being formed, or in the case both chlorine and water are present simultaneously, crosslinked compounds are formed, and these crosslinked compounds result in the problem of causing a decrease in vaporization stability.
An object of the present invention is to provide an organometallic compound capable of improving vaporization stability, its synthesis method, and a solution raw material and metal-containing thin film containing said compound.